Let's talk locations. What makes a good Jam location? When should we book it?
A Jam needs a physical location, organised by the host, where the Jam takes place. It might be an office, university, sports hall, appartment, boat, tent or taxicab. It will need enough space to host the Jam, sufficient heat, light, power, connectivity, some physical comforts and toilets. It would be good if food were available nearby - from a supermarket, restaurant or pizza guy, or even organised by the host. It will need to be accessible (or partly accessible) for the whole 48 hours* - the Jam is a global event, and the buzz goes round the clock.
If you want to encourage Jammers to make prototypes of physical things, you might want to have part of the space where they can make a mess, play with glue, use a hammer...
You do not need to find your location before you agree to host the Jam, but it might be a good idea to have some ideas for different sized spaces. When you see how many people your Jam attracts, you can decide which one to use.
* Note: If you cannot find a Jam location that is open around the clock, don't panic - this will not disqualify your Jam. However, experience shows that a 24-hour-open location is preferable, especially for larger Jams.